Euphausiids (krill) are globally significant zooplankton prey for many commercially important or endangered predator species. In the productive upwelling system of the Northern California Current (NCC), two krill species, Euphausia pacifica and Thysanoessa spinifera, dominate the preyscape and constitute an important food resource for many seabirds, cetaceans, and fish. In this study, we use five years of hydroacoustic and net tow data collected in the NCC to develop integrative models predicting acoustic backscatter scaled for E. pacifica or T. spinifera separately. Boosted Regression Trees and Generalized Additive Models are applied in an original ensemble hurdle framework to predict krill presence and abundance from a diverse set of topographic and oceanographic predictors. Krill metrics had significant relationships with seabed depth, distance to submarine canyons, and variables indicative of dynamic ocean conditions (e.g., total deviance explained in acoustic data: 25 % in the presence-absence model & 49 % in the abundance model). Predictions of krill abundance at 5 km resolution averaged by month indicate differential habitat preferences between the two species: T. spinifera was constrained to the continental shelf, around and inshore of the 200 m isobath, whereas E. pacifica was found in greater abundances just offshore of the 200 m isobath and into offshore water in lower abundances. E. pacifica was generally more abundant than T. spinifera (10:1.3 ratio). Both species increased in abundance in the spring and summer, followed by a rapid decline in the fall, and lowest abundances in the winter. These models can produce fine-scale spatial and year-round weekly predictions of E. pacifica and T. spinifera abundance in the NCC, which will provide essential knowledge and new spatial layers about critical ecosystem components to support research and management.

中文翻译：

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在北加利福尼亚洋流中使用缩放声学反向散射的 Euphausia pacifica 和 Thysanoessa spinifera 磷虾分布预测模型


磷虾 （Euphausiids） 是许多具有重要商业价值或濒危捕食物种的全球重要浮游动物猎物。在北加利福尼亚洋流 （NCC） 的生产性上升流系统中，两种磷虾物种 Euphausia pacifica 和 Thysanoessa spinifera 在猎物景观中占据主导地位，并构成了许多海鸟、鲸类动物和鱼类的重要食物资源。在这项研究中，我们使用在 NCC 中收集的五年水声和网拖数据来开发综合模型，分别预测 E. pacifica 或 T. spinifera 的声学反向散射比例。提升回归树和广义加法模型应用于原始的集成障碍框架中，以从各种地形和海洋学预测因子中预测磷虾的存在和丰度。磷虾指标与海底深度、到海底峡谷的距离以及指示动态海洋条件的变量（例如，声学数据中解释的总偏差：在存在-不存在模型中为 25%，在丰度模型中为 49%）。以每月平均的 5 公里分辨率对磷虾丰度的预测表明，两个物种之间的栖息地偏好不同：T. spinifera 仅限于大陆架、200 m 等深线周围和近海，而 E. pacifica 在 200 m 等深线近海发现的丰度较高，以较低的丰度进入近海水域。E. pacifica 通常比 T. spinifera 更丰富 （10：1.3 比例）。这两个物种在春季和夏季的丰度都有所增加，随后在秋季迅速下降，冬季的丰度最低。这些模型可以生成 E. pacifica 和 T 的精细空间和全年每周预测。 NCC 中的棘叶丰度，这将提供有关关键生态系统组成部分的基本知识和新的空间层，以支持研究和管理。